This is a study of the signal transmission properties of the neural network in the cat retina. Action potentials are recorded extracellularly from single retinal ganglion cells during different stimulus conditions. Stimuli which cause the retinal illumination to vary with time, and stimuli that results in variations of the retinal illumination with distance, as well as moving stimulus targets have been employed. For the past four years the main goal has been to find methods of stimulation by which it gets possible to elicit responses generated by one of the response mechanisms only; to study the properties of each mechanism in isolation and to investigate the manner in which the pure central and the pure surround inputs interact at the ganglion cell. In particular we have studied gain changes and spatial summation of adaptive effects within each individual mechanism. Only units of concentric center-surround organization have been studied.